Aqueous two-component polyurethane coating agent, process for its production, its use as a finishing coating material or clear coating material, and its use for coating plastics

ABSTRACT

The present invention relates to an aqueous two-component polyurethane coating composition comprising a component (I) wich contains as binder 
     (A1) at least one water-soluble or water-dispersible polyester resin (A1) which contains hydroxyl groups and acid groups which can be converted into the corresponding acid anion groups and has an OH number of from 30 to 250 mg of KOH/g and an acid number of from 5 to 150 mg of KOH/g, and 
     (A2) at least one water-soluble or water-dispersible polyurethane resin (A2) which contains hydroxyl groups and acid groups which can be converted into the corresponding acid anion groups and has an OH number of from 20 to 200 mg of KOG/g and an acid number of from 5 to 150 mg of KOH/g, and 
     (A3) at least one water-soluble or water-dispersible acrylate copolymer which contains hydroxyl groups and acid groups which can be converted into the corresponding acid anion groups, and/or an acrylated polyester and/or an acrylated polyurethane, which has an OH number of from 40 to 200 mg of KOG/g and an acid number of from 5 to 150 mg of KOH/g, and 
     (A4), if desired, at least one further polymer (A4) 
     and 
     II) a component (II) which contains a polyisocyanate component (F1) as crosslinking agent, wherein the mixing ratio of the polyester resin (A1) to the polyurethane resin (A2), expressed in parts by weight, is between 95:5 and 5:95.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to an aqueous two-component polyurethanecoating composition comprising

I.) a component (I) which contains as binder (A)

(A1) at least one water-soluble or water-dispersible polyester resin(A1) which contains hydroxyl groups and acid groups which can beconverted into the corresponding acid anion groups and has an OH numberof from 30 to 250 mg of KOH/g and an acid number of from 5 to 150 mg ofKOH/g, and

(A2) at least one water-soluble or water-dispersible polyurethane resin(A2) which contains hydroxyl groups and acid groups which can beconverted into the corresponding acid anion groups and has an OH numberof from 20 to 200 mg of KOH/g and an acid number of from 5 to 150 mg ofKOH/g, and

(A3) at least one water-soluble or water-dispersible acrylate copolymerwhich contains hydroxyl groups and acid groups which can be convertedinto the corresponding acid anion groups, and/or an acrylated polyesterand/or an acrylated polyurethane, which has an OH number of from 40 to200 mg of KOH/g and an acid number of from 5 to 150 mg of KOH/g, and(A4) if desired, at least one further polymer (A4) and

II.) a component (II) which contains a polyisocyanate component (F1) ascrosslinking agent.

The present invention also relates to a process for preparing theseaqueous coating compositions and to their use as a clearcoat or as atopcoat and to their use for coating plastics.

For ecological and economic reasons, the paint industry is seeking toreplace the amount of organic solvents used in paints as far as possibleby water. Aqueous coating compositions are already in use not only inthe area of automotive line coating but also in the area of automotiverepair finishes. In the area of plastic coating, too, it is increasinglydesirable to use aqueous systems, not only in the area of primers butalso in the area of topcoats.

Topcoats are understood to mean paints which are used for producing theuppermost paint coat. The uppermost paint coat can be a single-coat ormulticoat system, in particular a two-coat system. Two-coat topcoatsconsist of a pigmented basecoat layer and a clearcoat layer applied ontop of the basecoat layer, which clearcoat layer is unpigmented orpigmented only with transparent pigments. Nowadays two-coat paints areproduced by the wet-in-wet method in which a pigmented basecoat isprecoated and the resulting basecoat layer, without being subjected to abaking step, is overcoated with a clearcoat, and basecoat layer andclearcoat layer are then jointly cured. This method is very advantageousin terms of economics, but it makes high demands on the basecoat and theclearcoat. The clearcoat applied on top of the not yet cured basecoatmust not dissolve the basecoat layer on the surface or interfere in anyother way since this would lead to paints having poor appearance. Thisis in particular true of paints in which basecoats containing effectpigments (for example metallic pigments, in particular aluminum flakes,or nacreous pigments) are used.

In the area of plastic coating an additional requirement is that theresulting coatings should have high flexibility while exhibiting highmoisture resistance (for example low permeability). Furthermore, thecoatings should have good appearance. This means that the coatingsexhibit, for example, high gloss and that the coating compositions showgood flow properties. Furthermore the coatings should possess goodadhesion. In addition, component (I) of the coating composition shouldhave a long shelf life.

In the area of plastic coating, an additional requirement is that thecoating compositions used can be cured at low temperatures (in generalbelow 100° C.) and give films having the desired properties even whencured at these low temperatures.

DE-A-4,421,823 discloses aqueous polyurethane coating compositionsconsisting of at least three components where the component (I) containsat least one binder dissolved in organic solvent, which binder isselected from the group consisting of polyester resins, polyurethaneresins, polyacrylate resins and, if desired, of further binders;component (II) contains at least one uncapped polyisocyanate ascrosslinking agent; and component (III) is essentially free of binderand contains water. The coating compositions are prepared by mixing thethree components a short time before applying the coating compositions.These coating compositions are used, in particular, in the area ofautomotive repair finishes.

However, these coating compositions disclosed in DE-A-4,421,823 have thedisadvantage that their preparation is quite expensive since threedifferent components have to be stored and mixed with one another ashort time before applying the coating compositions. Furthermore, thiscoating composition contains a binder component which has beenpredissolved in an organic solvent, this solvent being also present inthe coating composition prepared from the three components.

Furthermore, DE-A-4,326,670 discloses aqueous two-component polyurethanecoating compositions based on an aqueous dispersion of at least onebinder having a number-average molecular weight of 1000 to 100,000 andcontaining groups which are reactive towards isocyanate groups,calculated on the basis of an OH number of 20 to 250 and an acid numberof 10 to 100, the acid functions of which are at least in partneutralized, and of a polyisocyanate as crosslinking agent. Examples ofsuitable binders include polyacrylate resins, polyester resins,polyurethane resins or (meth)acrylated polyester resins or(meth)acrylated polyurethane resins.

DE-A-4,326,670 does not describe the use of a mixture of at least onepolyester and at least one polyurethane resin and of at least onepolyacrylate resin or an acrylated polyester and/or an acrylatedpolyurethane as binder. The coating compositions disclosed inDE-A-4,326,670 have the disadvantage that their shelf life is notsufficiently long.

Accordingly, the object of the present invention is to provide aqueoustwo-component polyurethane coating compositions which are suitable forcoating plastic substrates, in particular in the area of the productionof topcoats. The resulting coatings should have, in particular, highelasticity while exhibiting high moisture resistance (for example lowpermeability). Furthermore, the coating compositions should meet therequirements usually demanded of coating compositions which are used forcoating plastic substrates. Accordingly, the coating compositionsshould, for example, also give coatings having good appearance (goodgloss, good flow properties, and the like) and good adhesion.Furthermore, component (I) of the coating composition should have a longshelf life.

Finally, the coating compositions should be curable at low temperatures(in general below 100° C.) and should give films having the desiredproperties even when cured at these low temperatures.

Surprisingly, this object is achieved by means of the coatingcompositions of the type mentioned at the beginning, wherein the mixingratio of the polyester resin (A1) to the polyurethane resin (A2) isbetween 95 parts by weight of polyester resin: 5 parts by weight ofpolyurethane resin and 5 parts by weight of polyester resin: 95 parts byweight of polyurethane resin.

The present invention also provides a process for preparing thesecoating compositions and relates to the use of the coating compositionsas topcoat or clearcoat and to their use for coating plastics.

It is surprising and was not foreseeable that the use of a mixture of atleast one polyacrylate resin and/or acrylated polyester and/or acrylatedpolyurethane resin and at least one polyester resin and at least onepolyurethane resin as binder would result in aqueous two-componentpolyurethane coating compositions which give coatings which, not onlywith respect to flexibility but also simultaneously with respect tomoisture resistance, have improved properties compared with coatingsprepared by using at least one polyacrylate resin and/or acrylatedpolyester and/or acrylated polyurethane resin and either at least onepolyester resin or at least one polyurethane resin.

An additional advantage is that the coating compositions according tothe invention result in coatings having good appearance and goodadhesion. Furthermore, component (I) of the coating composition exhibitsa long shelf life, and the coating compositions show good applicationperformance. Finally, the coating compositions are curable at lowtemperatures (in general below 100° C.) and lead to films having thedesired properties even when cured at these low temperatures.

DETAILED DESCRIPTION OF THE INVENTION

Below, first the individual components of the coating compositionsaccording to the invention are described in more detail.

It is essential to the invention that the coating composition containsas binder a mixture of at least one polyacrylate resin and/or oneacrylated polyester and/or one acrylated polyurethane resin and at leastone water-soluble or water-dispersible polyester resin (A1) and at leastone water-soluble or water-dispersible polyurethane resin (A2), themixing ratio of the polyester resin (A1) to the polyurethane resin (A2)being between 95 parts by weight of polyester resin: 5 parts by weightof polyurethane resin and 5 parts by weight of polyester resin: 95 partsby weight of polyurethane resin. Preferred coating compositions areobtained if the mixing ratio of polyester resin (A1) to polyurethaneresin (A2) is between 90 parts by weight of polyester resin: 10 parts byweight of polyurethane resin and 30 parts by weight of polyester resin70 parts by weight of polyurethane resin, particularly preferablybetween 75 parts by weight of polyester resin: 25 parts by weight ofpolyurethane resin and 50 parts by weight of polyester resin: 50 partsby weight of polyurethane resin.

Suitable polyester resins (A1) for preparing the coating compositionsaccording to the invention are all water-soluble or water-dispersiblepolyester resins (A1) which contain hydroxyl groups and acid groupswhich can be converted into the corresponding acid anion groups, whichpolyester resins have an OH number of from 30 to 250 mg of KOH/g,particularly preferably of from 60 to 200 mg of KOH/g, and an acidnumber of from 5 to 150 mg of KOH/g, preferably of from 15 to 75 mg ofKOH/g, and particularly preferably of from 20 to 50 mg of KOH/g.Polyester resins (A1) preferably have number-average molecular weightsMn of between 500 and 30,000 Dalton, preferably of between 1000 and10,000 Dalton, and particularly preferably of between 1000 and 5000Dalton, in each case measured against a polystyrene standard. It ispreferred to use branched polyesters.

Preferably, those polyesters are used which are obtainable by reacting

p1) di- and/or polycarboxylic acids or esterifiable derivatives thereof,if desired together with monocarboxylic acids,

p2) diols,

p3) polyolols, if desired together with monools, and

p4) if desired further modifying components.

Of these, polyesters which have been prepared without using monools andmonocarboxylic acids are particularly preferably used. Polyesters whichare free of unsaturated fatty acids are also particularly preferred.

Examples of polycarboxylic acids which can be used as component (p1)include aromatic, aliphatic and cycloaliphatic polycarboxylic acids.Preferably, aromatic and/or aliphatic polycarboxylic acids are used ascomponent (p1).

Examples of suitable polycarboxylic acids are phthalic acid, isophthalicacid, terephthalic acid, halophthalic acid, such as tetrachloro- ortetrabromophthalic acid, adipic acid, glutaric acid, azelaic acid,sebacic acid, fumaric acid, maleic acid, trimellitic acid, pyromelliticacid, tetrahydrophthalic acid, hexahydrophthalic acid,1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid,1,4-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic acid,endomethylenetetrahydrophthalic acid, tricyclodecanedicarboxylic acid,endoethylenehexahydrophthalic acid, camphoric acid,cyclohexanetetracarboxylic acid, cyclobutanetetracarboxylic acid andothers. The cycloaliphtatic [sic] polycarboxylic acids can be usedeither in their cis or in their trans form and as a mixture of bothforms. The esterifiable derivatives of the abovementioned polycarboxylicacids, such as, for example, mono- or polyesters thereof with aliphaticalcohols having 1 to 4 carbon atoms or hydroxyalcohols having 1 to 4carbon atoms, are also suitable. In addition, the anhydrides of theabovementioned acids, if they exist, can also be used.

Examples of monocarboxylic acids which, if desired, can be used togetherwith the polycarboxylic acids, are benzoic acid, tert-butylbenzoic acid,lauric acid, isononanoic acid and hydrogenated fatty acids of naturallyoccurring oils, preferably isononanoic acid.

Examples of suitable diols (p2) for preparing the polyester (A2) areethylene glycol, propanediols, butanediols, hexanediols, neopentylglycolhydroxypivalate, neopentylglycol, diethylene glycol, cyclo-hexanediol,cyclohexanedimethanol, trimethylpentanediol and ethylbutylpropanediol.Furthermore, aliphatic polyether diols, such as linear or branchedpoly(oxyethylene) glycols, poly(oxypropylene) glycols and/orpoly(oxybutylene) glycols, and mixed polyether diols, such aspoly(oxyethyleneoxypropylene) glycols, are also suitable. The polyetherdiols usually have a molecular weight Mn of 400 to 3000.

Furthermore, the diols used can also be aromatic or alkylaromatic diols,such as, for example, 2-alkyl-2-phenylpropane-1,3-diol, bisphenolderivatives having ether functionality, and the like.

Further suitable diols include esters of hydroxycarboxylic acids withdiols where the abovementioned diols can be used as the diol. Examplesof hydroxycarboxylic acids are hydroxypivalic acid ordimethylolpropanoic acid.

Examples of polyols which are suitable as component (p3) areditrimethylolpropane, trimethylolethane, trimethylolpropane, glycerol,pentaerythritol, homopentaerythritol, dipentaerythritol,tris(hydroxyethyl) isocyanate, 1,2,4 butanetriol [sic], propane- andhexanetriols, trihydroxycarboxylic acids, such astris(hydroxymethyl)(ethyl)ethanoic acids. Polyols having at least 3 OHgroups can be used on their own or as a mixture. If desired, the triolscan be used together with monohydric alcohols, such as, for example,butanol, octanol, lauryl alcohol, cyclohexanol, tert-butylcyclohexanol,ethoxylated and propoxylated phenols.

Suitable components (p4) for preparing the polyesters (A1) are inparticular compounds containing a group which is capable of reactingwith the functional groups of the polyester. Their modifying components(p4) used can be diepoxide compounds, if desired also monoepoxidecompounds. Examples of suitable components (p4) are described inDE-A-4,024,204 on page 4, lines 4 to 9.

Suitable components (p4) for preparing the polyesters (A1) includecompounds which also contain, in addition to a group which is capable ofreacting with the functional groups of the polyester (A1), a tertiaryamino group, for example monoisocyanates containing at least onetertiary amino group or mercapto compounds containing at least onetertiary amino group. For details, see DE-A-4,024,204, page 4, lines 10to 49.

Polyesters (A1) are prepared by the known esterification methods, suchas described, for example, in DE-A-4,024,204, page 4, lines 50 to 65.

This reaction is usually carried out at temperatures of between 180 and280° C., if desired in the presence of a suitable esterificationcatalyst, such as, for example, lithium octoate, dibutyltin oxide,dibutyltin dilaurate, para-toluenesulfonic acid, and the like. Thepreparation of the polyesters (A1) is usually carried out in thepresence of small amounts of a suitable solvent which is used asentrainer. Examples of the entrainer used are aromatic hydrocarbons,such as, in particular, xylene and (cyclo)aliphatic hydrocarbons, forexample cyclohexane. However, another alternative is to prepare thepolyesters in the absence of solvents (solvent-free reaction)

Particularly preferably, the components (A1) used are polyesters whichhave been prepared by a two-step process by first preparing ahydroxyl-containing polyester having an OH number of from 100 to 400 mgof KOH/g, preferably of from 150 to 350 mg of KOH/g, and an acid numberof less than 10 mg of KOH/g and a number-average molecular weight Mn offrom 500 to 2000 Dalton which is then reacted in a second step withcarboxylic anhydrides to give the desired polyester (A1). The amount ofcarboxylic anhydrides is selected such that the polyester obtained hasthe desired acid number. Suitable acid anhydrides are those which areusually used for this reaction, such as, for example, hexahydrophthalicanhydride, trimellitic anhydride, pyromellitic anhydride, phthalicanhydride, camphoric anhydride, tetrahydrophthalic anhydride, succinicanhydride and mixtures of these and/or other anhydrides and, inparticular, anhydrides of aromatic polycarboxylic acids, such astrimellitic anhydride.

Apart from being reacted with carboxylic anhydrides, the acid groups canfurthermore also be incorporated in the polyester by usingdimethylolpropionic acid and the like.

The polyurethane resins (A2) used for preparing the coating compositionsaccording to the invention include any polyurethane resins (A2) whichcontain water-soluble or water-dispersible hydroxyl groups and acidgroups which can be converted into the corresponding acid anion groupsand have an OH number of from 20 to 200 mg of KOH/g, preferably of from80 to 180 mg of KOH/g, and an acid number of from 5 to 150 mg of KOH/g,in each case relative to the solid resin. Preferably, the polyurethaneresins used are those having a number-average molecular weight Mn ofbetween 1000 and 30,000 Dalton, preferably of between 1000 and 15,000Dalton, and particularly preferably of between 1000 and 7500 Dalton, ineach case measured against a polystyrene standard.

Suitable polyurethane resins are described, for example, in thefollowing publications: EP-A-355,433, DE-A-3,545,618, DE-A-3,813,866,DE-A-3,210,051, DE-A-2,624,442, DE-A-3,739,332, U.S. Pat. No. 4,719,132,EP-A-89,497, U.S. Pat. No. 4,558,090, U.S. Pat. No. 4,489,135,DE-A-3,628,124, EP-A-158,099, DE-A-2,926,584, EP-A-195,931,DE-A-3,321,180 and DE-A-4,005,961.

The polyurethane resins which can be used in component (I) are thosewhich are preparable by reacting isocyanato-containing prepolymers withcompounds which are capable of reacting with isocyanate groups.

The isocyanato-containing prepolymers can be prepared by reactingpolyols having a hydroxyl number of from 10 to 1800, preferably from 50to 1200, mg of KOH/g with excess polyisocyanates at temperatures of upto 150° C., preferably 50 to 130° C., in organic solvents which areincapable of reacting with isocyanates. The equivalent ratio of NCO toOH groups is between 2.0:1.0 and >1.0:1.0, preferably between 1.4:1 and1.1:1.

The polyols used for preparing the prepolymer can be of low molecularweight and/or of high molecular weight and contain inert anionic groupsor groups capable of forming anions or cationic groups or groups whichare capable of forming cations. The additional use oflow-molecular-weight polyols having a molecular weight of from 60 to 400Dalton for preparing the isocyanato-containing prepolymers is alsopossible. The amounts of polyols used can be up to 30% by weight,preferably about 2 to 20% by weight, relative to the total amount ofpolyol components.

To obtain an NCO prepolymer of high flexibility, a large amount of apredominantly linear polyol having a preferred OH number of from 30 to150 mg of KOH/g should be added. Up to 970 by weight of the total amountof polyol can consist of saturated and unsaturated polyesters and/orpolyethers having a number-average molecular weight Mn of from 400 to5000 Dalton. The polyether diols selected should not introduce excessiveamounts of ether groups since otherwise the polymers formed will besubject to swelling in water. Polyester diols are prepared byesterifying organic dicarboxylic acids or anhydrides thereof withorganic diols or are derived from a hydroxycarboxylic acid or from alactone. Branched polyester polyols can be prepared by using smallamounts of polyols or polycarboxylic acids having a relatively highnumber of hydroxyl or carboxyl groups.

The NCO prepolymer contains at least about 0.5% by weight of isocyanategroups, preferably at least 1% by weight of NCO, relative to solids. Theupper limit is about 15% by weight, preferably 10% by weight,particularly preferably 5% by weight of NCO.

However, the compounds which are preferably used are polyurethane resins(A2) which are available by reacting in a first reaction step

(a) at least one organic di- and/or polyisocyanate with

(b) at least one compound containing at least one group which is capableof reacting with isocyanate groups and at least one group which ensureswater dispersibility, preferably one group which is capable of forminganions,

to give a reaction product having free isocyanate groups which is thenreacted with

(c) a polycondensation product comprising

(k1) 10 to 45 mol % of at least one diol,

(k2) 5 to 50 mol % of at least one polyol having at least 3 OH groupsper molecule,

(k3) 35 to 47 mol % of at least one di- and/or polycarboxlic acid, ifdesired together with a monocarboxylic acid, and

(k4) 0 to 20 mol % of at least one monool, the sum of the mol % of thecomponents (k1) to (k4) being in each case 100 mol %, and

(d) 0 to 20 mol %, relative to component c, of further alcoholcomponents

to give the polyurethane resin (A2), the amounts of components (a) to(d) being selected such that the polyurethane resin has the desired OHnumbers and acid numbers and, if desired, the desired molecular weights.

Particularly preferred polyurethane resins are obtained by usingcomponents (k1), (k2), (k3) and (k4) in such molar ratios that the sumof the OH building blocks (k1), (k2) and (k4) combined and the sum ofthe COOH building blocks (k4) are used [sic] in the ratio of 0.8:1 to1.6:1.

The relative amounts of components (a) to (d) can be selected to varyover wide ranges and as a function of the reaction components. Ifpolyester component (c) does not contain any hydrophilic segments, suchas polyether portions, it is preferred to react up to 1.1 mol ofpolyester (c) per mole of NCO equivalent to give an OH/NCO ratio of >1.If a polymeric polyester containing hydrophilic segments is used, it isalso possible to use more than 1.1 mol of polyester (c) per NCOequivalent.

Suitable multifunctional isocyanates for preparing the polyurethaneresins include aliphatic, cycloaliphatic and/or aromatic polyisocyanatescontaining at least two isocyanate groups per molecule. Preference isgiven to isomers or mixtures of isomers of organic diisocyanates. Owingto their good resistance to UV light, (cyclo)aliphatic diisocyanatesyield products of low tendency to yellowing. The polyisocyanatecomponent needed for forming the polyurethane resin can also contain aproportion of polyisocyanates of higher valence, provided this does notlead to gel formation. Triisocyanates which have successfully beenemployed are those products which are obtained by trimerization oroligomerization of diisocyanates or by reaction of diisocyanates withpolyfunctional compounds containing OH or NH groups. If desired, theaverage functionality can be lowered by adding monoisocyanates.

Examples of polyisocyanates which can be used are phenylenediisocyanate, toluylene diisocyanate, xylylene diisocyanate,bisphenylene diisocyanate, naphthylene diisocyanate, diphenylmethanediisocyanate, isophorone diisocyanate, cyclobutane diisocyanate,cyclopentylene diisocyanate, cyclohexylene diisocyanate,methylcyclohexylene diisocyanate, dicyclohexylmethane diisocyanate,ethylene diisocyanate trimethylene diisocyanate, tetramethylenediisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate,propylene diisocyanate, ethylethylene diisocyanate and trimethylhexanediisocyanate.

High-solid polyurethane resin solutions are prepared by using, inparticular, diisocyanates of the general formula (III′)

where X is a divalent aromatic hydrocarbon radical, preferably anunsubstituted or halo-, methyl- or methoxy-substituted naphthylene,diphenylene or 1,2-, 1,3- or 1,4-phenylene radical, particularlypreferably a 1,3-phenylene radical, and R₁ and R₂ are an alkyl radicalhaving 1-4 carbon atoms, preferably a methyl radical. Diisocyanates ofthe formula (III′) are known (their preparation is described, forexample, in EP-A-101,832, U.S. Pat. No. 3,290,350, U.S. Pat. No.4,130,577 and U.S. Pat. No. 4,439,616), and are in part commerciallyavailable (1,3-bis)l-isocyanatoprop-2-yl)benzene is sold, for example,by the American Cyanmid [sic] Company under the trade name TMXDI(META)®). Further preferred polyisocyanate components are diisocyanatesof the formula (IV′):

where R is a divalent alkyl or aralkyl radical having 3 to 20 carbonatoms and R′ is a divalent alkyl or aralkyl radical having 1 to 20carbon atoms.

In general, polyurethanes are not compatible with water unless specificcomponents have been incorporated during the synthesis and/or specificpreparative steps have been carried out. Thus, the compounds used forpreparing not only the preferred polyurethane resins prepared by theabovementioned two-step process but also for preparing otherpolyurethane resins used as component (A2) are those containing at leastone group which is capable of reacting with isocyanate groups and atleast one group which ensures water dispersibility. Suitable groups ofthis type are non-ionic groups (e.g. polyethers), anionic groups,mixtures of these two groups or cationic groups.

Thus, it is preferred to incorporate in the polyurethane resin an acidnumber sufficient for dispersing the neutralized product in water togive a stable dispersion. The compounds used for this purpose are thosecontaining at least one group which is capable of reacting withisocyanate groups and at least one group which is capable of forminganions. Suitable groups which are capable of reacting with isocyanategroups are in particular hydroxyl groups and primary and/or secondaryamino groups. Groups which are capable of forming anions are carboxyl,sulfonic acid and/or phosphonic acid groups. Preferably, alkanoic acidscontaining two substituents on the alpha-carbon atom are used. Thesubstituent can be a hydroxyl group, an alkyl group or an alkylol group.These polyols one, contain at least usually 1 to 3, carboxyl groups permolecule. They contain two to about 25, preferably 3 to 10, carbonatoms. Very particular preference is given to using dimethylolpropanoicacid. The carboxyl-containing polyol can make up to 1 to 25% by weight,preferably 1 to 20% by weight, of the total amount of polyol componentsin the polyurethane resin (A2).

The amount of ionizable carboxyl groups available in salt form as aresult of the neutralization of the carboxyl groups is usually at least0.4% by weight, preferably at least 0.7% by weight, relative to solids.The upper limit is about 12% by weight. The amount of dihydroxyalkanoicacids in the unneutralized prepolymer gives an acid number of at least 5mg of KOH/g, preferably at least 10 mg of KOH/g. If the acid numbers arevery low, further measures for achieving water dispersibility areusually necessary. The upper limit of the acid number is 150 mg ofKOH/g, preferably 40 mg of KOH/g, relative to solids. The acid number ispreferably in the range of from 20 to 40 mg of KOH/g.

As for the compounds (k1) to (k4) which are suitable for preparing thepolycondensation product (c) and as for the reaction conditions used intheir preparation, see the description of the polyester resins (A1).

The polycondensation products (c) which are preferably used are thosehaving an OH number of from 100 to 400 mg of KOH/g, preferably of from150 to 300 mg of KOH/g, an acid number of from 0 to 50 mg of KOH/g,preferably of from 0 to 30 mg of KOH/g, and particularly preferably of 1to 20 mg of KOH/g, in each case relative to the solid resin, and anumber-average molecular weight Mn of between 500 and 15,000 Dalton,preferably of between 1000 and 10,000 Dalton, in each case measuredagainst a polystyrene standard.

Examples of alcohol components which are suitable as further modifyingcomponents (d) are monoalcohols, such as nonanol and decanol, andreaction products of monocarboxylic acids with epoxides. Preferably, thecomponents (d) are compounds having on average more than 1 OH group permolecule.

The polyurethane resins can be prepared by the known methods (e.g.acetone method). Alternatively, the components can also be reacted inethoxyethyl propionate (EEP) as solvent. The amount of ethoxyethylpropionate can vary over a wide range and should be sufficient forobtaining a prepolymer solution of suitable viscosity. In general, up to70% by weight, preferably 5 to 50% by weight, and particularlypreferably less than 20% by weight, of solvent, relative to solids, areused. Thus, for example, it is particularly preferred to carry out thereaction at a solvent content of 10-15% by weight of EEP, relative tosolids.

If desired, the reaction of the components can be carried out in thepresence of a catalyst, such as organotin compounds and/or tertiaryamines.

The coating compositions according to the invention contain as component(A3) at least one water-soluble or water-dispersible acrylate copolymerwhich contains hydroxyl groups and acid groups which can be convertedinto the corresponding acid anion groups and/or one acrylated polyesterand/or one acrylated polyurethane having an OH number of from 40 to 200mg of KOH/g and an acid number of from 5 to 150 mg of KOH/g.

The acrylate copolymers used as component (A3) preferably havenumber-average molecular weights of between 1000 and 30,000 Dalton,preferably of between 1000 and 15,000 Dalton, in each case measuredagainst a polystyrene standard.

Acrylate copolymers which are suitable as acrylate copolymer (A3)containing hydroxyl groups and acid groups include all those having theOH numbers, acid numbers and molecular weights mentioned.

Acrylate copolymers which are preferably used as component (A3) arethose which are obtainable by polymerization of

a1) a (meth)acrylate which is different from (a2), (a3), (a4), (a5) and(a6), copolymerizable with (a2), (a3), (a4), (a5) and (a6) andsubstantially free of acid groups or a mixture of such monomers,

a2) an ethylenically unsaturated monomer which is copolymerizable with(a1), (a3), (a4), (a5) and (a6), different from (a5) and carries atleast one hydroxyl group per molecule and is substantially free of acidgroups, or a mixture of such monomers,

a3) an ethylenically unsaturated monomer which carries, per molecule, atleast one acid group which can be converted into the corresponding acidanion group, and is copolymerizable with (a1), (a2), (a4), (a5) and(a6), or a mixture of such monomers, and

a4) if desired one or more vinyl esters of alpha-branched monocarboxylicacids having 5 to 18 carbon atoms per molecule, and/or

a5) if desired at least one reaction product of acrylic acid and/ormethacrylic acid with the glycidyl ester of an alpha-branchedmonocarboxylic acid having 5 to 18 carbon atoms per molecule or, insteadof the reaction product, an equivalent amount of acrylic and/ormethacrylic acid which is then reacted, during or after thepolymerization reaction, with the glycidyl ester of an alpha-branchedmonocarboxylic acid having 5 to 18 carbon atoms per molecule,

a6) if desired an ethylenically unsaturated monomer which iscopolymerizable with (a1), (a2), (a3), (a4) and (a5), is different from(a1), (a2), (a4) and (a5) and is substantially free of acid groups, or amixture of such monomers

in an organic solvent or a solvent mixture and in the presence of atleast one polymerization initiator,

type and amount of (a1), (a2), (a3), (a4), (a5) and (a6) being selectedsuch that polyacrylate resin (A3) has the desired OH number, acid numberand the desired molecular weight.

In order to prepare the polyacrylate resins used according to theinvention, the component (a1) used can be any (meth)acrylic ester whichis coplymerizable with (a2), (a3), (a4), (a5) and (a6) and issubstantially free of acid groups or a mixture of such (meth)acrylicesters. Examples include alkyl acrylates and alkyl methacrylates havingup to 20 carbon atoms in the alkyl radical, such as, for example, methylacrylate and methacrylate, ethyl acrylate and methacrylate, propylacrylate and methacrylate, butyl acrylate and methacrylate, hexylacrylate and methacrylate, ethylhexyl acrylate and methacrylate, stearylacrylate and methacrylate and lauryl acrylate and methacrylate, andcycloaliphatic (meth)acrylic esters, such as, for example, cyclohexyl(meth)acrylate, isobornyl (meth)acrylate, dicyclopentaene [sic](meth)acrylate and tert-butylcyclohexyl (meth)acrylate.

The component (a1) used can also be ethyltriglycol (meth)acrylate andmethoxyoligoglycol (meth)acrylate having a number-average molecularweight Mn of, preferably, 550 Dalton or other ethoxylated and/orpropoxylated hydroxyl-free (meth)acrylic acid derivatives.

The compounds which are used as component (a2) can be ethylenicallyunsaturated monomers which are copolymerizable with (a1), (a2), (a3),(a4), (a5) and (a6), are different from (a5), carry at least onehydroxyl group per molecule and are substantially free of acid groups,or can be a mixture of such monomers. Examples include hydroxyalkylesters of acrylic acid, methacrylic acid or any otheralpha,beta-ethylenically unsaturated carboxylic acid. These esters canbe derived from an alkylene glycol which is esterified with the acid orthey can be obtained by reacting the acid with an alkylene oxide. Thecompounds which are used as component (a2) are preferably hydroxyalkylesters of acrylic acid or methacrylic acid in which the hydroxyalkylgroup contains up to 20 carbon atoms, reaction products of cyclicesters, such as, for example, epsilon-caprolactone, with thesehydroxyalkyl esters, or mixtures of these hydroxyalkyl esters or ofhydroxyalkyl esters modified with epsilon-caprolactone.

Examples of such hydroxyalkyl esters include 2-hydroxyethyl acrylate,2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxypropylmethacrylate, 3-hydroxypropyl methacrylate, 2-hydroxyethyl methacrylate,4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, hydroxystearylacrylate and hydroxystearyl methacrylate. The corresponding esters ofother unsaturated acids, such as, for example, ethacrylic acid, crotonicacid and similar acids having up to about 6 carbon atoms per molecule,can also be used.

Furthermore olefinically unsaturated polyols can also be used ascomponent (a2). Preferred polyacrylate resins (A3) are obtained by usingtrimethylolpropane monoallyl ether at least in part as component (a2).The proportion of trimethylolpropane monoallyl ether is usually 2 to 10%by weight, relative to the total weight of the monomers (a1) to (a6)used for preparing the polyacrylate resin. However, in addition to this,it is also possible to add 2 to 10% by weight of trimethylolpropanemonoallyl ether, relative to the total weight of the monomers used forpreparing the polyacrylate resin, to the finished polyacrylate resin.The olefinically unsaturated polyols, such as, in particular,trimethylolpropane monoallyl ether, can be used as the onlyhydroxyl-containing monomers, but are used in particular proportionatelyin a combination with others of the hydroxyl-containing monomersmentioned.

The component (a3) used can be any ethylenically unsaturated monomerwhich carries at least one acid group, preferably a carboxyl group, permolecule and is copolymerizable with (a1), (a2), (a4), (a5) and (a6), ora mixture of such monomers. The component (a3) used is particularlypreferably acrylic acid and/or methacrylic acid. However, otherethylenically unsaturated carboxylic acids having up to 6 carbon atomsin the molecule can also be used. Examples of such acids includeethacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconicacid. Furthermore, for example, ethylenically unsaturated sulfonic orphosphonic acids or partial esters thereof can be used as component(a3). Mono(meth)acryloyloxyethyl maleate, mono(meth)acryloyloxyethylsuccinate and mono(meth)acryloyloxyethyl phthalate can also be used ascomponent (a3).

The component (a4) used includes one or more vinyl esters ofalpha-branched monocarboxylic acids having 5 to 18 carbon atoms in themolecule. The branched monocarboxylic acids can be obtained by reactingformic acid or carbon monoxide and water with olefins in the presence ofa liquid, strongly acid catalyst. The olefins can be products obtainedby cracking paraffinic hydrocarbons, such as mineral oil fractions, andcan contain not only branched but also straight-chain acyclic and/orcylcoaliphatic olefins. The reaction of such olefins with formic acid orwith carbon monoxide and water produces a mixture of carboxylic acids inwhich the carboxyl groups are predominantly attached to a quaternarycarbon atom. Examples of other olefinic starting materials are propylenetrimer, propylene tetramer and diisobutylene. However, the vinyl esterscan also be prepared from the acids in the manner known per se, forexample by reacting the acid with acetylene.

Owing to their ready availability, it is particularly preferred to usevinyl esters of saturated aliphatic monocarboxylic acids which contain 9to 11 carbon atoms and are branched on the alpha-carbon atom.

The compound which is used as component (a5) is the reaction product ofacrylic acid and/or methacrylic acid with the glycidyl ester of analpha-branched monocarboxylic acid having 5 to 18 carbon atoms permolecule. Glycidyl esters of highly branched monocarboxylic acids areavailable under the trade name “Cardura”. The reaction of the acrylic ormethacrylic acid with the glycidyl ester of a carboxylic acid having atertiary alpha-carbon atom can take place before, during or after thepolymerization reaction. Preferably, the component (a5) used is thereaction product of acrylic and/or methacrylic acid with the glycidylester of versatic acid. This glycidyl ester is commercially availableunder the name “Cardura E10”.

The compounds which can be used as component (a6) include anyethylenically unsaturated monomers which are copolymerizable with (a1),(a2), (a3), (a4) and (a5), are different from (a1), (a2), (a3) and (a4)and are substantially free of acid groups, or mixtures of such monomers.Preferably, vinylaromatic hydrocarbons, such as styrene,alpha-alkylstyrenes and vinyltoluene, are used as component (a6).

The compounds which can be used as component (a6) include polysiloxanemacromonomers in combination with other monomers mentioned as beingsuitable as component (a6). Suitable polysiloxane macromonomers arethose having a number-average molecular weight Mn of from 1000 to40,000, preferably of from 2000 to 10,000 Dalton and on average 0.5 to2.5, preferably 0.5 to 1.5, of ethylenically unsaturated double bondsper molecule. Examples of suitable polysiloxane macromonomers are thosedescribed in DE-A 3,807,571 on pages 5 to 7, in DE-A 3,706,095 incolumns 3 to 7, in EP-B 358,153 on pages 3 to 6 and in U.S. Pat. No.4,754,014 in columns 5 to 9. Furthermore, other vinyl monomerscontaining acryloxysilane and having the abovementioned molecularweights and contents of ethylenically unsaturated double bonds, forexample compounds obtainable by reacting hydroxy functional silanes withepichlorohydrin, followed by reacting the reaction product withmethacrylic acid and/or hydroxyalkyl esters of (meth)acrylic acid, arealso suitable.

Preferably, the polysiloxane macromonomers mentioned in DE-A 4,421,823are used as component (a6).

Examples of polysiloxane macromonomers which are suitable as component(a6) include the compounds mentioned in the international patentapplication, application number WO 92/22615 on page 12, line 18, to page18, line 10.

The amount of the polysiloxane macromonomer(s) (a6) used for modifyingthe acrylate copolymers (A1) is less than 5% by weight, preferably 0.05to 2.5% by weight, particularly preferably 0.05 to 0.8% by weight, ineach case relative to the total weight of the monomers used forpreparing copolymer (A3).

By using such polysiloxane macromonomers, the slip of the aqueouscoating compositions according to the invention is improved.

Particularly preferably used acrylate resins are obtained bypolymerization of

(a1) 20 to 60% by weight, preferably 30 to 50% by weight, of component(a1),

(a2) 10 to 40% by weight, preferably 15 to 35% by weight, of component(a2),

(a3) 1 to 15% by weight, preferably 2 to 8% by weight, of component(a3),

(a4) 0 to 25% by weight, preferably 5 to 15% by weight, of component(a4),

(a5) 0 to 2ir by weight, preferably 5 to 15% by weight, of component(a5), and

(a6) 5 to 30% by weight, preferably 10 to 20% by weight, of component(a6),

the sum of the weight proportions of components (a1) to (a6) being ineach case 100% by weight.

The preparation of the polyacrylate resins (A3) used according to theinvention is carried out in an organic solvent or solvent mixture and inthe presence of at least one polymerization initiator. The organicsolvents and polymerization initiators used are the solvents andpolymerization initiators customary for preparing polyacrylate resinsand suitable for preparing aqueous dispersions. The solvents used canparticipate in the reaction with the crosslinking component (II) andthus act as reactive diluent.

Examples of useful solvents are butylglycol, 2-methoxypropanol,n-butanol, methoxybutanol, n-propanol, ethylene glycol monomethyl ether,ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,diethylene glycol diethyl ether, diethylene glycol monobutyl ether,trimethylolpropane, ethyl 2-hydroxypropionate and3-methyl-3-methoxybutanol and derivatives based on propylene glycol, forexample ethyl ethoxypropionate, isopropoxypropanol, methoxypropylacetate and the like. Alternatively, the polyacrylate resins (A3) canalso be prepared first in a solvent which is not water-dilutable andthen, if desired, to replace this solvent after polymerization in partby a water-dilutable solvent.

Examples of useful polymerization initiators include free-radicalinitiators, such as, for example, tert-butylperoxyethyl hexanoate,benzoyl peroxide, azobisisobutyronitrile and tert-butyl perbenzoate.Preferably, the initiators are used in an amount of 2 to 25% by weight,particularly preferably in an amount of 4 to 10% by weight, relative tothe total weight of the monomers.

Polymerization is advantageously carried out at a temperature of from 80to 160° C., preferably from 110 to 160° C. Preferably, the solvents usedare n-butanol, ethoxyethyl propionate and isopropoxypropanol.

Polyacrylate resin (A3) is preferably prepared by a two-step processsince in this way the resulting aqueous coating compositions exhibitbetter processability. Accordingly, it is preferred to use polyacrylateresins which are obtainable by

1. polymerizing a mixture of (a1), (a2), (a4), (a5) and (a6) or amixture of portions of components (a1), (a2), (a4), (a5) and (a6) in anorganic solvent,

2. adding, after at least 60% by weight of the mixture comprising (a1),(a2), (a4), (a5) and, if present, (a6) have been added, (a3) and anyremainder of components (a1), (a2), (a4), (a5) and (a6) and continuingpolymerization, and

3. after completion of the polymerization, neutralizing the resultingpolyacrylate resin, if desired, at least in part, i.e. converting theacid groups into the corresponding acid anion groups.

However, it is also possible to introduce first components (a4) and/or(a5) together with at least a portion of the solvent and then to meterin the remaining components. Another possibility is to introducecomponents (a4) and/or (a5) only in part together with at least aportion of the solvent into the reaction vessel and to add the remainderof these components as described above. It is preferred to introducefirst, for example, at least 20% by weight of the solvent and about 10%by weight of components (a4) and (a5) and, if desired, portions ofcomponents (a1) and (a6). Preference is also given to preparing thepolyacrylate resins (A3) used according to the invention by a two-stepprocess in which step (I) has a duration of 1 to 8 hours, preferably of1.5 to 4 hours, and the mixture comprising (a3) and any remainder ofcomponents (a1), (a2), (a4), (a5) and (a6) is added over a period of 20to 120 minutes, preferably over a period of 30 to 90 minutes. Afteraddition of the mixture comprising (a3) and any remainder of components(a1), (a2), (a4), (a5) and (a6) is complete, polymerization is continueduntil conversion of all monomers used is essentially complete.

The amount and rate of addition of the initiator is preferably selectedsuch that a polyacrylate resin (A3) having the desired number-averagemolecular weight is obtained. It is preferred to start the initiatorfeed some time, in general about 15 minutes, before the monomer feed.Preference is furthermore given to a process in which addition of theinitiator is started at the same time as addition of the monomers and iscompleted about half an hour after addition of the monomers has beencompleted. The initiator is preferably added in a constant amount perunit of time. After addition of the initiator is complete, the reactionmixture is maintained at the polymerization temperature for a time(usually 1.5 hours) sufficient for essentially complete conversion ofall monomers used. “Essentially complete conversion” is understood asmeaning that preferably 1000 by weight of monomers used have beenconverted and that, however, it is also possible that a small residualmonomer content of not more than about 0.50% by weight, relative to theweight of the reaction mixture, may remain unconverted.

Preferably, the monomers for preparing polyacrylate resins (A3) arepolymerized at a polymerization solids content which is not excessivelyhigh, preferably at a polymerization solids content of 80 to 50% byweight, and the solvents are then in part removed by distillation togive polyacrylate resin solutions having a solids content of,preferably, 80 to 60% by weight.

Suitable components (A3) are furthermore acrylated polyesters having anOH number of from 40 to 200 mg of KOH/g, particularly preferably of from60 to 160 mg of KOH/g, and an acid number of from 5 to 150 mg of KOH/g,preferably of from 15 to 75 mg of KOH/g, and particularly preferably offrom 20 to 50 mg of KOH/g. The acrylated polyesters (A3) preferably havenumber-average molecular weights Mn of between 1000 and 50,000 Dalton,preferably of between 1000 and 15,000 Dalton, in each case measuredagainst a polystyrene standard. The acrylated polyesters which are usedas component (A3) are known. Suitable acrylated polyesters (A3) can beprepared by various processes known to one skilled in the art, forexample by incorporating trimethylolpropane monoallyl ether or maleicanhydride or other reactive anhydrides which are polymerizable withstyrene and/or (meth)acrylates, followed by acrylation (organic oraqueous).

Suitable components (A3) furthermore include acrylated polyurethaneshaving an OH number of from 40 to 200 mg of KOH/g, particularlypreferably of from 60 to 160 mg of KOH/g, and an acid number of from 5to 150 mg of KOH/g, preferably of from 15 to 75 mg of KOH/g, andparticularly preferably of from 20 to 50 mg of KOH/g. The acrylatedpolyurethanes (A3) preferably have number-average molecular weights Mnof between 1000 and 50,000 Dalton, preferably of between 1000 and 15,000Dalton, in each case measured against a polystyrene standard. Theacrylated polyurethanes which are used as component (A3) are also known.Examples of suitable acrylated polyurethanes are described, for example,in DE-A-4,122,265, page 2, line 15, to page 5, line 44, inDE-A-4,010,176, page 2, line 41, to page 6, line 64, in EP-A-308,115,page 2, line 29, to page 5, line 21, in EP-A-510,572, page 3, line 21,to page 5, line 42, and in U.S. Pat. No. 4,496,708, column 4, line 5, tocolumn 12, line 46.

Suitable components (A4) include any polymers which are compatible withthe remaining constituents of component (I). For example, the di- and/orpolyisocyanates mentioned as examples of suitable crosslinking agentscan be used in capped form as (A4). Illustrative examples of cappingagents for the di- and/or polyisocyanates mentioned include aliphatic,cycloaliphatic or aralipatic monoalcohols, such as, for example, methylalcohol, butyl alcohol, octyl alcohol, lauryl alcohol, cyclohexanol orphenylcarbinol, hydroxylamines, such as ethanolamine, oximes, such asmethyl ethyl ketone oxime, acetone oxime or cyclohexanone oxime, amines,such as dibutylamine or diisopropylamine, malonic diesters, ethylacetoacetate and/or epsilon-caprolactam.

Component (I) preferably contains as binder (A) a mixture of

10 to 50% by weight of the mixture of at least one polyester (A1) and atleast one polyurethane resin (A2),

50 to 90% by weight of at least one polyacrylate resin (A3) and/or of atleast one acrylated polyester resin and/or of at least one acrylatedpolyurethane resin and

0 to 10% by weight of at least one further polymer (A4),

the sum of the weight proportions of the components being in each case100% by weight.

Furthermore, it is preferable to use binders (A) (i.e. the mixture ofcomponents (A1) to (A4)) which have an OH number of from 50 to 200,preferably of from 80 to 180, mg of KOH/g.

The component (I) can contain as further constituent (B) any pigmentscustomary for paints in amounts of 0 to 60% by weight, relative tocomponent I. The pigments can be composed of inorganic or organiccompounds and can be effect pigments and/or coloring pigments.

Effect pigments which can be used include metal flake pigments, such ascommercially available aluminum bronzes, aluminum bronzes chromated inaccordance with DE-A-3,363,183, and commercially available stainlesssteel bronzes and non-metallic effect pigments, such as, for example,nacreous or interference pigments. Examples of suitable inorganiccoloring pigments are titanium dioxide, iron oxides, Sicotrans yellowand carbon black. Examples of suitable organic coloring pigments areindanthrene blue, Cromophtal red, Irgazine orange and Heliogene green.

Component (I) and also the binder can contain as further constituent (C)at least one organic partially or completely water-soluble solvent. Suchsolvents can also participate in the reaction with crosslinkingcomponent (II) and thus act as reactive diluent. Examples of suitablesolvents are the compounds already mentioned for the preparation of thepolyacrylate resins (A3) (see above). Further suitable solvents areesters, ketones, keto esters, glycol ether esters and glycol ethers, forexample ethylene glycol and 1,2- and 1,3-propylene glycol.

Furthermore, solvents (C) can entirely or in part consist oflower-molecular-weight oligomeric compounds which may be capable ofreacting with crosslinking component (II) or else may also be incapableof reacting with them. Solvents (C) are usually used in an amount of 0to 20% by weight, preferably in an amount of less than 15% by weight,relative to the total weight of component (I).

Component (I) usually contains as constituent (D) at least oneneutralizing agent. Examples of suitable neutralizing agents areammonia, ammonium salts, such as, for example, ammonium carbonate orammonium bicarbonate, and amines, preferably tertiary amines, such as,for example, trimethylamine, triethylamine, tributylamine,dimethylaniline, diethylaniline, triphenylamine, dimethylethanolamine,diethylethanolamine, methyldiethanolamine, triethanolamine, and thelike. The neutralizaing agent used is particularly preferablydimethylethanolamine.

The overall amount of neutralizing agent used in the coating compositionaccording to the invention is selected such that 1 to 100 equivalents,preferably 50 to 90 equivalents, of acid groups of the binder (A) areneutralized.

Component (I) can contain as constituent (E) at least onerheology-regulating additive. Examples of rheology-regulating additivesinclude crosslinked polymer microparticles, such as disclosed, forexample, in EP-A-38,127, inorganic layer silicates, such as, forexample, aluminum magnesium silicates, sodium magnesium layer silicatesand sodium magnesium fluorine lithium layer silicates of themontmorillonite type, and synthetic polymers containing ionic and/orassociative groups, such as polyvinyl alcohol, poly(meth)acrylamide,poly(meth)acrylic acid, polyvinylpyrrolidone, styrene/maleic anhydridecopolymers or ethylenelmaleic anhydride copolymers and derivativesthereof or else hydrophobically modified ethoxylated urethanes orpolyacrylates. Preferably, the rheology-regulating additives used arepolyurethanes. Component (I) preferably contains 0 to 2.0% by weight ofthe rheology-regulating additive, relative to the total weight ofcomponent (I).

In addition, component (I) can contain at least one further customarypaint additive. Examples of such additives are defoamers, dispersingaids, emulsifiers and flow-control agents.

Finally, component (I) additionally contains water. Paint component (II)contains as crosslinking agent at least one di- and/or polyisocyanate(F1) which may or may not be dissolved in one or more organic solvent ormay or may not be dispersed in water-dilutable solvents and ispreferably uncapped.

The polyisocyanate component (F1) can be any organic polyisocyanatecontaining aliphatically, cycloaliphatically, araliphatically and/oraromatically bonded free isocyanate groups. Preferably, thepolyisocyanates used have 2 to 5 isocyanate groups per molecule andviscosities of from 100 to 2000 mPas (at 23° C). If desired, smallamounts of organic solvent, preferably 1 to 25% by weight, relative tothe pure polyisocyanate, can be added to the polyisocyanates to improvethe incorporability of the isocyanate and, if desired, to lower theviscosity of the polyisocyanate to a value within the abovementionedranges. Examples of solvents for the polyisocyanates which are suitableas additives are ethoxyether propionate, butyl acetate, and the like.

Examples of suitable isocyanates are described, for example, in“Methoden der organischen Chemie” (Methods of organic chemistry),Houben-Weyl, Volume 14/2, 4th Edition, Georg Thieme Verlag, Stuttgart1963, pp. 61 to 70, and by W. Siefken, Liebigs Ann. Chem. 562, 75 to136. Suitable isocyanates are, for example, the isocyanates mentioned inthe description of the polyurethane resins (A2) and/orisocyanato-containing polyurethane prepolymers which can be obtained byreaction of polyols with excess polyisocyanate and are preferably of lowviscosity.

It is also possible to use polyisocyanates which contain isocyanurategroups and/or biuret groups and/or allophanate groups and/or urethanegroups and/or urea groups and/or uretdione groups. Polyisocyanates whichcontain urethane groups are obtained, for example, by reacting a portionof the isocyanate groups with polyols, such as, for example,trimethylolpropane and glycerol.

Preferably, the isocyanates used are aliphatic or cycloaliphaticpolyisocyanates, in particular hexamethylene diisocyanate, dimerized andtrimerized hexamethylene diisocyanate, isophorone diisocyanate,2-isocyanatopropylcyclohexyl isocyanate, dicyclohexylmethane2,4′-diisocyanate or dicyclohexylmethane 4,4′-diisocyanate or mixturesof these polyisocyanates. Very particular preference is given to usingmixtures of polyisocyanates which are based on hexamethylenediisocyanate and contain uretdione and/or isocyanurate groups and/orallophanate groups, as obtained by catalytic oligomerization ofhexamethylene diisocyanate in the presence of suitable catalysts.Incidentally, the polyisocyanate component (F1) can also comprise anydesired mixtures of the polyisocyanates mentioned by way of example.

Advantageously, polyisocyanate component (F1) is used in the coatingcompositions according to the invention in such an amount that the ratioof the hydroxyl groups of binder (A) to the isocyanate groups ofcrosslinking agent (F1) is between 1:2 and 2:1, particularly preferablybetween 1:1 and 1:1.5.

The two components (I) and (II) of the coating composition according tothe invention are prepared from the individual constituents withstirring using customary methods. The preparation of the coatingcomposition from these two components (I) and (II) is likewise effectedby stirring or dispersing using the customarily used apparatuses, forexample using dissolvers or the like or using the likewise customarilyused 2-component metering and blending unit or using the method forpreparing aqueous 2-component polyurethane coatings described inDE-A-19,510,651, page 2, line 62, to page 4, line 5.

The aqueous coatings prepared using the binders according to theinvention usually contain in their ready-to-use state 30 to 80,preferably 45 to 70, % by weight of water, 0 to 50, preferably 0 to 20,% by weight of organic solvents, 6 to 70, preferably 15 to 70, % byweight of binder (A) according to the invention, preferably 0 to 25% byweight of pigments and/or fillers and 0 to 10% by weight of otheradditives, such as, for example, catalysts, thickeners, flow-controlagents, and the like, their percentages by weight given being based onthe entire formulation of the coatings in the ready-to-use state (i.e.,for example with respect to their spray viscosity).

The aqueous coatings prepared using the binders according to theinvention can be used for coating primed or unprimed plastics, such as,for example, ABS, AMMA, ASA, CA, CAB, EP, UF, CF, MF, MPF, PF, PAN, PA,PC, PE, HDPE, LDPE, LLDPE, UHMWPE, PET, PMMA, PP, PS, SB, PUR, PVC, RF,SAN, PBT, PPE, POM, PUR-RIM, SMC, BMC, PP-EPDM and UP (abbreviations inaccordance with DIN 7728T1). The plastics to be coated can of coursealso be polymer blends, modified plastics or fiber-reinforced plastics.The coating compositions according to the invention are preferably usedfor coating PPE/PA blends, polycarbonate blends (e.g. PC/ASA, PC/PBT)and polypropylene blends. The coating compositions according to theinvention are used in particular for plastics customarily used in theconstruction of vehicles, in particular in the construction of motorizedvehicles.

Non-functionalized and/or non-polar substrate surfaces have to besubjected to a pretreatment, such as plasma or flame, prior to coating.

Suitable primers include any customary primers, not only conventionalprimers but also aqueous primers. It is of course also possible to useradiation-curable primers and radiation-curable aqueous primers.

The coating compositions according to the invention are used forproducing a single-layer or multi-layer coating and preferably astopcoats. However, they can also be used as a clearcoat on top of abasecoat, for example as a clearcoat of a multi-layer coating preparedby the wet-in-wet method. It is of course also possible to coat theplastics or the other substrates directly with the clearcoat or thetopcoat.

Finally, the coating compositions can also be applied to othersubstrates, such as, for example, metal, wood or paper. They are appliedby customary methods, for example spraying, knife-coating, dipping orbrushing.

The coating compositions according to the invention are usually cured attemperatures of below 120° C., preferably at temperatures of at most100° C. In special application forms of the coating compositionsaccording to the invention, it is also possible to employ higher curingtemperatures.

The coating compositions according to the invention are preferably usedfor producing topcoats. The coating compositions according to theinvention can be used not only in line coating but also in repairfinishes of automotive bodies. However, they are preferably used in thearea of repair finishes and very particularly preferably in the coatingof plastic parts.

Below, the invention is illustrated in more detail by means of exemplaryembodiments. All parts given are parts by weight unless expressly statedotherwise.

1.1. Preparation of a dispersion of a polyester resin (A1)

7.43 kg of hexanediol, 25.72 kg of neopentyl glycol hydroxypivalate,4.23 kg of trimethylolpropane, 16.99 kg of hexahydrophthalic anhydride,0.016 kg of hydrated tin oxide and 2.529 kg of cyclohexane are weighedinto a steel vessel suitable for polycondensation reactions, and themixture is heated at a maximum product temperature of 220° C. for a timesufficiently long to reach an acid number of from 6 to 8 and an OHnumber of about 276. After the acid number has been reached, the mixturewas cooled to 120° C., and 9.06 kg of trimellitic anhydride are added.Heating to no more than 160° C. is continued until reaching an acidnumber of 35. The mixture was then cooled to 80° C., and 8.15 kg ofisopropoxypropanol were added. This was followed by adding at thistemperature 2.62 kg of dimethylethanolamine. Finally, a dispersion wasprepared having an acid number of 35 and a solids content of 35%, adimethylethanolamine content of 1.83% and a solvent content of 6.29% byadding deionized water. The polyester resin (A1) had an OH number of 143mg and an acid number of 36.4 mg of KOH/g, in each case relative to thesolid resin.

1.2. Preparation of a dispersion of polyurethane resin (A2)

Polyester precursor

To prepare 1 kg of polyester, 128.9 g of neopentyl glycol, 318.9 g ofneopentyl glycol hydroxypivalate, 166.0 g of trimethylolpropane, 205.5 gof isophthalic acid, 40 g of xylene and 254.3 g of hexhydrophthalic[sic] anhydride were weighed into a steel vessel suitable forpolycondensation reactions, the mixture was continually heated up, andthe water of condensation was removed continuously. As soon as theproduct had reached an acid number of 3, the reaction was stopped, andthe mixture was cooled to 100° C. and partially dissolved with methylethyl ketone (MEK) until reaching a solids content of 80% (viscosity ofthe 50% solution in MEK 0.2 Pas.). The condensation product thusobtained had an OH number of 202 mg of KOH/g and an acid number of 3.5mg of KOH/g, in each case relative to the solid resin.

Urethane-modified polyester dispersion 1:

488.4 g of meta-tetramethylxylylene diisocyanate, 134.1 g ofdimethylolpropoinic [sic] acid and 568.0 g of methyl ethyl ketone areweighed into a steel vessel suitable for polyaddition reactions, and themixture was heated to 80° C. At a constant isocyanate content of 7.4%,relative to the mixture used, the batch was cooled to 50° C., and 2110 gof the polyester solution were added. This was followed by heating to80° C. At an isocyanate content of <0.1% and a viscosity of 3.6 dPas(10.3 in N-methylpyrolidone [sic]), the mixture was neutralized with71.2 g of N,N-dimethylethanolamine. It is then diluted with water, andthe organic solvent is removed in vacuo. Finally, it is brought to asolids content of 43% by adding deionized water. The pH of thedispersion was 6.8. The dispersion was speckle-free, homogenous and hada shelf life of at least 8 weeks at 50° C. The DMEA content was 1.42%and the solvent content 0.5%. The polyurethane resin had an OH number of98 mg of KOH/g, an acid number of 26 mg of KOH/g and a number-averagemolecular weight of 1713, measured against a polystyrene standard andbased on the solid resin.

1.3. Preparation of a dispersion of an acrylate resin (A3)

A 4 l steel reactor equipped with two monomer feeds, initiator feed,stirrer and reflux condenser was charged with 470 parts by weight ofn-butanol as solvent component (B2) (water solubility WS: 9.0,evaporation rate ER: 33, boiling point b.p.: 118° C.), and the mixtureis heated to 110° C. This was followed by addition of a solution of 36parts by weight of tert-butylperoxyethyl hexanoate in 92.4 parts byweight of n-butanol (B2) at such a rate that addition is complete after5.5 hours. At the same time at which addition of thetert-butylperoxyethyl hexanoate solution is started, addition of themixture comprising (a1) to (a6):

(a1): 240 parts by weight of n-butyl methacrylate,

 209 parts by weight of methyl methacrylate,

 120 parts by weight of lauryl methacrylate (methacrylic ester 13 fromRöhm GmbH),

(a2): 270 parts by weight of hydroxyethyl methacrylate and

(a6): 180 parts by weight of styrene

is also started. The mixture comprising (a1), (a2) and (a6) is added atsuch a rate that addition is complete after 5 hours.

3.5 hours after the first monomer feed was started, a second monomerfeed is started which is completed jointly with the first monomer feedand consists of a mixture of monomer components (a2) and (a5):

(a2): 120 parts by weight of hydroxyethyl methacrylate and

(a5): 61 parts by weight of acrylic acid.

After addition of the tert-butylperoxyethyl hexanoate solution iscomplete, the reaction mixture is maintained at 120° C. for another 2 h.The resin solution is then cooled to 80° C. and neutralized with 63parts by weight of dimethylethanolamine in 1379 parts by weight [lacuna]to a degree of neutralization of 85% within about 30 minutes.

The solvent (B) n-butanol is then removed by azeotropic distillationuntil not more than 1% by weight of (B), relative to the dispersion, canbe detected by gas chromatography.

After distillation is complete, the dispersion is adjusted to thefollowing final characteristic values by addition of deionized water:

acid number of the entire solid: 37.2 mg of KOH/g,

solids content (1 hour, 130° C.): 38.3%, pH: 7.40.

Dimethylethanolamine content: 2.11%

Solvent content: 0.52%

The acrylate resin (A3) thus prepared had a number-average molecularweight of 7772 Dalton and a weight-average molecular weight of 26,651,measured against a polystyrene standard, an OH number of about 140 mg ofKOH/g and an acid number of 37.2 mg of KOH/g, in each case relative tothe solid resin.

2. Preparation of the coating compositions from Examples 1 to 3 and fromComparative Examples 1 and 2

The coating compositions are prepared from the components listed inTable 1 by preparing first component (I) from components (K-I-1) through(K-I-15) and component (II) from components (K-I—1) through (K-II-2) ineach case by mixing using a laboratory stirrer, then mixing components(I) and (II), and finally bringing the mixture to the viscositymentioned by addition of water.

The coating compositions thus prepared are applied pneumatically to PPpanels (dry film thickness 30-35 micrometers). The panels thus coatedare baked at 90° C. for 45 minutes and then aged at 22° C. and 50% ofrelative humidity of air for 8 days. The free clearcoat films are thensubjected to various tests. The test results of the coatings aresummarized in Tables 2 and 3.

Furthermore, the coating compositions of Examples 1 to 3 aredistinguished by very good optical properties (appearance). Moreover,components (I) of Examples 1 to 3 have a long shelf life of at leasthalf a year at 23° C. or of at least 8 weeks at 40° C.

SUMMARY OF THE TEST RESULTS

Examples 1 to 3 show that by using a mixture of polyester resin andpolyurethane resin as further binder result [sic] in coatings havinghigh elasticity (high elongation at break values at a relatively highbreaking force) while exhibiting low permeability.

TABLE 1 Composition of the coating compositions of Examples 1 to 3 andof Comparative Examples 1 and 2 in parts by weight Comp. Comp. Ex. 1 Ex.2 Ex. 3 1 2 PES (A1) K-I-1 12.16 9.12 6.08 18.24 — PUR (A2) K-I-2 4.957.42 9.90 — 14.85 PAC (A3) K-I-3 64.7 64.7 64.7 65.21 65.21 BGA K-I-44.899 4.899 4.899 4.899 4.899 IPP K-I-5 0.868 1.059 1.251 0.769 1.633PnB K-I-6 3.267 3.267 3.267 3.267 3.267 Water K-I-7 5.452 5.827 6.2003.909 6.439 Dil. K-I-8 1.955 1.955 1.955 1.955 1.955 Emul. K-I-9 0.6520.652 0.652 0.652 0.652 Wett. 1 K-I-10 0.938 0.938 0.938 0.938 0.938Wett. 2 K-I-11 0.078 0.078 0.078 0.078 0.078 Flow-c. K-I-12 0.078 0.0780.078 0.078 0.078 Light s. 1 K-I-13 0.155 0.155 0.155 0.155 0.155 Lights. 2 K-I-15 0.271 0.271 0.271 0.271 0.271 Sum — 100 100 100 100 100 SCBI — 31.17 31.17 31.17 31.17 31.17 SC (A1)/ — 2.000 1.000 0.500 — — SC(A2) Isocyan. K-II-1 21.60 21.38 21.16 21.96 20.73 EEP K-II-2 5.40 5.345.29 5.49 5.18 Water K-III 15.00 15.00 15.00 15.00 15.00 viscos. OH(SC)/ — 0.717 0.717 0.717 0.717 0.717 NCO (mol)

Explanation of Table 1

PES (A1): Polyester dispersion (A1) described in 1.1

PUR (A2): Polyurethane dispersion (A2) described in 1.2

PAC (A3): Polyacrylate dispersion (A3) described in 1.3

BGA: 2-Butoxyethyl acetate

IPP: 1(2)-Isopropoxy-2(1)-propanol

PnB: 1(2)-Butoxy-2(1)-propanol

Dil.: 10% solution of a commercially available thickener based onpolyglycol dialkyl ether in water

Emul.: Commercially available emulsifier based on polyglycol octylphenolether

Wett. 1: Commercially available polyether-modified dimethyloligosiloxane

Wett. 2: Commercially available polyether-modified dimethylpolysiloxane

Flow-c.: Commercially available flow-control agent based on apolyether-modified polysiloxane

Light s. 1: Commercially available light stabilizer based on asterically hindered amine (HALS)

Light s. 2: Commercially available light stabilizer based onbenzotriazole

Isocyan.: Commercially available 100% pure isocyanate based on ahexamethylene diisocyanate allophanate having an NCO content of 20%

SC(BI): Solids content of the binder, sum of (A1)+(A2)+(A3)

EEP: Ethoxyethyl propionate

Water visc.: Water added for adjusting the viscosity

OH(SC)/NCO (mol): Ratio of the OH groups of the binder (sum of(A1)+(A2)+(A3)) to the NCO groups of the crosslinking agent

TABLE 2 Test results of permeability (100 micrometers x g x m⁻² x d⁻¹)to water vapor 40° C. Comparative Ex. 1 121 Example 1 61 Example 2 68.8Example 3 63.5 Comparative Ex. 2 74.5

TABLE 3 Test results of the mechanical properties Comp. 1 Ex. 1 Ex. 2Ex. 3 Comp. 2 Breaking 5.4 6.7 8.4 7 8.7 force (N) Elong. at 19 20 22 139 break (%) Elong. 10 8 5.5 5 4.5 Fmax (%)

Explanation of Tables 2 and 3:

The permeability to water vapor was determined on water-saturated foamsat 40° C. using the carrier gas method.

Furthermore, characteristic values of the free films were determined ina ZWICK universal testing apparatus by subjecting them to atensile/elongation test. The values given are the breaking force in N,the elongation at break in % and the elongation at Fmax in

What is claimed is:
 1. An aqueous two-component polyurethane coatingcomposition comprising (I) a component (I) comprising a binder (A)comprising (A1) at least one water-soluble or water-dispersiblepolyester resin comprising hydroxyl groups and acid groups which can beconverted into the corresponding acid anion groups, wherein said resinhas an OH number of from 30 to 250 mg of KOH/g and an acid number offrom 5 to 150 mg of KOH/g, (A2) at least one water-soluble orwater-dispersible polyurethane resin comprising hydroxyl groups and acidgroups which can be converted into the corresponding acid anion groups,wherein said resin has an OH number of from 20 to 200 mg of KOH/g and anacid number of from 5 to 150 mg of KOH/g, (A3) a resin having an OHnumber of from 40 to 200 mg of KOH/g and an acid number of from 5 to 150mg of KOH/g selected from the group consisting of at least onewater-soluble or water-dispersible acrylate copolymer comprisinghydroxyl groups and acid groups which can be converted into thecorresponding acid anion groups, an acrylated polyester, an acrylatedpolyurethane, and mixtures thereof, and (A4) optionally, at least onefurther polymer, and (II) a component comprising a free polyisocyanatecomponent (F1) as crosslinking agent, wherein the mixing ratio of thepolyester resin (A1) to the polyurethane resin (A2) is between 95 partsby weight of polyester resin: 5 parts by weight of polyurethane resinand 5 parts by weight of polyester resin: 95 parts by weight ofpolyurethane resin.
 2. The aqueous coating composition of claim 1,wherein the mixing ratio of polyester resin (A1) to polyurethane resin(A2) is between 90 parts by weight of polyester resin: 10 parts byweight of polyurethane resin and 30 parts by weight of polyester resin:70 parts by weight of polyurethane resin.
 3. The aqueous coatingcomposition of claim 1, wherein the polyurethane resin (A2) is obtainedby reacting in a first reaction step (a) at least one organic isocyanateselected from the group consisting of diisocyanates, polyisocyanates,and mixtures thereof, with (b) at least one compound comprising at leastone group reactive with isocyanate groups and at least one group whichensures water dispersibility, to give a reaction product having freeisocyanate groups which is then reacted with (c) a polycondensationproduct comprising (k1) 10 to 45 mol % of at least one diol, (k2) 5 to50 mol % of at least one polyol having at least 3 OH groups permolecule, (k3) 35 to 47 mol % of at least one carboxylic acid selectedfrom the group consisting of dicarboxylic acids, polycarboxylic acids,and mixtures thereof, and optionally one or more monocarboxylic acids,(k4) 0 to 20 mol % of at least one monool, the sum of the mol % of thecomponents (k1) to (k4) being in each case 100 mol %, and (d) 0 to 20mol %, relative to component (c), of at least one further alcoholcomponent to give polyurethane resin (A2).
 4. The coating composition ofclaim 1, wherein binder (A) comprises 10 to 50% by weight of the mixturecomprising at least one polyester (A1) and at least one polyurethaneresin (A2), 50 to 90% by weight of at least one resin (A3) and 0 to 10%by weight of at least one further polymer (A4), the sum of the weightproportions of the components being in each case 100% by weight.
 5. Thecoating composition of claim 1, wherein (A3) comprises an acrylatecopolymer obtained by polymerizing (a1) a (meth)acrylate which isdifferent from (a2), (a3), (a4), (a5), and (a6), copolymerizable with(a2), (a3), (a4), (a5), and (a6), and substantially free of acid groupsor a mixture of such monomers, (a2) an ethylenically unsaturated monomerwhich is copolymerizable with (a1), (a3), (a4), (a5), and (a6),different from (a5), and carries at least one hydroxyl group permolecule and is substantially free of acid groups, or a mixture of suchmonomers, (a3) an ethylenically unsaturated monomer which carries, permolecule, at least one acid group and is copolymerizable with (a1),(a2), (a4), (a5), and (a6), or a mixture of such monomers, (a4)optionally, one or more vinyl esters of alpha-branched monocarboxylicacids having 5 to 18 carbon atoms per molecule, (a5) optionally, atleast one member selected from the group consisting of the reactionproduct of an acid selected from the group consisting of acid,methacrylic acid, and mixtures thereof, with the glycidyl ester of analpha-branched monocarboxylic acid having 5 to 18 carbon atoms permolecule, an equivalent amount of an acid selected from the groupconsisting of acrylic acid, methacrylic acid, and mixtures thereof,which is reacted, during or after the polymerization reaction, with theglycidyl ester of an alpha-branched monocarboxylic acid having 5 to 18carbon atoms per molecule, (a6) optionally, an ethylenically unsaturatedmonomer which is copolymerizable with (a1), (a2), (a3), (a4) and (a5),is different from (a1), (a2), (a3), (a4), and (a5), and is substantiallyfree of acid groups, or a mixture of such monomers, in one or moreorganic solvents in the presence of at least one polymerizationinitiator.
 6. The coating composition of claim 1, wherein the polyesterresin (A1) is obtained by reacting p1) one or more members selected fromthe group consisting of dicarboxylic acids, polycarboxylic acids,esterifiable derivatives thereof, and mixtures thereof, and optionallyone or more monocarboxylic acids, p2) diols, p3) polyols, and optionallyone or more monools, p4) optionally further modifying components.
 7. Thecoating composition of claim 1, wherein the polyurethane resin (A2) isobtained by using one or more diisocyanates selected from the groupconsisting of diisocyanates of the general formula (III′)

wherein x is a divalent aromatic hydrocarbon radical, and R₁ and R₂ arean alkyl radical having 1-4 carbon atoms, diisocyanates of the generalformula (IV′):

where R is a divalent alkyl or aralkyl radical having 3 to 20 carbonatoms and R′ is a divalent alkyl or aralkyl radical having 1 to 20carbon atoms, and mixtures thereof.
 8. The coating composition of claim1, wherein the binders (A1) through (A4) and the crosslinking agent (F1)are used in such amounts that the equivalent ratio of hydroxyl groups ofcomponents (A1) through (A4) of binder (A) to the isocyanate groups ofthe crosslinking agent (F 1) is between 1:2 and 2:1.
 9. A process forpreparing the coating composition of claim 1, comprising mixing thebinder-containing component (I) and the crosslinking agent-containingcomponent (II) before application of the coating composition.
 10. Aprocess of coating a substrate, comprising applying a coatingcomposition of claim 1 to a substrate.
 11. The process of claim 10,wherein the substrate is previously coated and the coating compositionof claim 1 is a topcoat.
 12. The aqueous coating composition of claim 2,wherein the mixing ratio of polyester resin (A1) to polyurethane resin(A2) is between 75 parts by weight of polyester resin: 25 parts byweight of polyurethane resin and 50 parts by weight of polyester resin:50 parts by weight of polyurethane resin.
 13. The aqueous coatingcomposition of claim 3, wherein compound (b) comprises at least onegroup which ensures water dispersibility and is capable of forminganions.
 14. The aqueous coating composition of claim 3, whereincomponent (k3) includes one monocarboxylic acid.
 15. The coatingcomposition of claim 4, wherein binder (A) has an OH number of from 50to 200 mg of KOH/g.
 16. The coating composition of claim 15, whereinbinder (A) has an OH number of from 80 to 180 mg of KOH/g.
 17. Thecoating composition of claim 6, wherein component p1) includes one ormore monocarboxylic acids.
 18. The coating composition of claim 6,wherein component p3) includes one or more monools.
 19. The coatingcomposition of claim 7, wherein x is a radical selected from the groupconsisting of an unsubstituted naphthylene, halo-substitutednaphthylene, methyl-substituted naphthylene, methoxy-substitutednaphthylene, diphenylene, 1,2-phenylene, 1,3-phenylene, and1,4-phenylene.
 20. The coating composition of claim 19 wherein x is a1,3-phenylene radical.
 21. The coating composition of claim 7, whereinR₁ and R₂ are a methyl radical.
 22. The coating composition of claim 8,wherein the binders (A1) through (A4) and the crosslinking agent (F1)are used in such amounts that the equivalent ratio of hydroxyl groups ofcomponents (A1) through (A4) of binder (A) to the isocyanate groups ofthe crosslinking agent (F1) is between 1:1.2 and 1:1.5.